This invention relates to apparatus and methods for the effective construction of laser tubes and associated apparatus. More particularly, it relates to the fabrication and installation of laser lens and mirror components.
As laser apparatus moves gradually from the status of scientific curiosity into the realm of large scale commercial applications, more stringent requirements are generally being imposed. As in any field, increasing demands are being placed on the durability and reliability of the lasers. Moreover, designers and ultimate users are increasingly demanding laser apparatus which performs in accordance with well defined and rigidly controlled specifications, and which furthermore maintains performance within the specifications over a long useful life span. Finally, more and more applications are being developed in which polarized coherent light is called for.
Within the foregoing framework of general demands being placed upon lasers, manufacturers perpetually are seeking laser designs, components, and fabrication methods which not only produce apparatus of the desired characteristics, but furthermore which may be produced economically, preferably on a large scale, mass-production basis.
The present invention is directed to achieving the foregoing specification and quality control goals, while operating on a profitable production basis. Furthermore, the principles of the present invention are also directed to solution of many of the more particular problems faced in the laser production business, some of which are as follows.
After the laser structure is generally assembled, but prior to evacuation and insemination with the lasing gases, it is desirable to purify the elements with a fast, hot, dry bake. Ideally, the parameters of this step are sufficient to drive out all parasitic substances which later might interact with, and cause the plasma to decompose with use. In accordance with the present state of the art, however, which typically seals lenses and mirrors to the tube either by means of a glass frit or epoxy resin, the use of the purifying bake step is necessarily limited. For example, epoxies typically possess a coefficient of thermal expansion as much as an order of magnitude larger than that of glass. Furthermore, the glass itself may be subjected to displacement or bending upon application of heat, thereby vitiating any adjustment in the laser tube.
It is therefore one specific object of the present invention to afford laser materials and components which are relatively impervious to conditions experienced in purification bakes of laser materials.
With regard to the optical components themselves, very specific and rigid requirements apply. First, it is necessary that lens and mirror components have a perfect or near perfect optical finish. This includes a smooth unblemished surface as well as an internal composition having a virtually zero density of striae. Moreover, when installed, the lenses and mirrors must be relatively strain free. It is clear that even in a perfect optical component, if unduly stressed when installed in the laser tube, birefringence will occur, thereby diminishing operational effectiveness. While the balance between overly tight installation, and risk of birefringence, is a severe one, it is correspondingly apparent that if the optical component is installed too loosely, the instrument may lase intermittently or not at all. It is preferable, furthermore, that epoxies be avoided as a sealant, since when subjected to heat either in the fabrication process or during operation, organic vapors are produced which interact wtih the plasma, causing it also to decompose. If these organic materials are still present after completion of fabrication, deposits will eventually form on the mirror and lens elements of the laser, with consequent degradation of power. Finally, it is desirable that optical components, once permanently installed, be amenable to various techniques for adjustment of the instrument to optimum lasing conditions.
It is accordingly a further object of the principles of the present invention to afford optical components and methods for installation of the same which achieve, as nearly as possible, the foregoing specific operational requirements.
Finally, it is to be noted that, notwithstanding the increasingly exacting specification burden placed upon manufacturers, overall production efficiency and economy always is mandated. It is accordingly a further object of the present invention that optical components be produced, installed, and adjusted to achieve the desird operating conditions in the most economical way available.